1. Field of the Invention
The invention relates to a process for the selection, in a vehicle, of traffic information received or to be sent. The selection is carried out in dependence on the type of road on which the vehicle is travelling. The invention also relates to a device for implementing this process.
2. Description of the Prior Art
Collecting data on and describing a traffic situation is an essential task in the field of traffic telematics, the goal of which is to eliminate and avoid traffic congestion to the greatest extent possible by directing drivers in advance to less crowded roads. For this purpose, the use of stationary collection devices installed at the roadside (e.g., distance markers, induction loops, etc.) is known. However, this involves great expense for creating and maintaining the required infrastructure; it is also disadvantageous that such devices, depending on the system, have extremely limited local ranges of use. To collect data about the traffic situation throughout a wide area, it is therefore necessary to install a huge number of collection devices.
Recent attempts to collect data on the traffic situation without the use of permanently installed roadside devices are also known. In such systems information is sent from the vehicles of a sampling fleet to collection points (e.g., traffic direction centers). In effect, this creates measurement station that move along with the traffic ("floating probes") and transmit relevant data (especially vehicle speed) via mobile wireless communications devices (e.g., mobile phones) to individual data collection points for further processing and evaluation. The results can then be sent to a large number of drivers in the form of traffic advice and recommendations for alternate routes, so that drivers can make the best possible decision, depending on the traffic situation, about the routes to choose.
Often, individual tasks in traffic telematics are limited to certain traffic segments, e.g., long-distance traffic on highways or city traffic. In collecting traffic data, it is of interest to have the relevant traffic information sent to the data collection points only from those vehicles that are located on a particular given type of road. Advantageously, this is done in a fully automatic manner by suitable terminal devices in the vehicles of a sampling fleet. In this way, the load placed on the data channels of the communications system being used can be kept within tolerable limits. It should be possible for each vehicle to autonomously recognize the road type.
This process requires a suitable location-finding system to determine the current position of a vehicle; for example, devices based on navigation satellites. In addition, it has been necessary until now for a digitized road map to be carried along in the vehicle, from which, in reference to the positional data supplied by the location-finding system, the actual road being travelled on could be determined by appropriate "map matching." However, difficulties can result from the fact that the determination of position is subject to a certain imprecision, which can be so great that often no unambiguous assignment of the current position to one of several possible roads (closely adjacent) is possible. Furthermore, carrying along a digitized road map (e.g., on CD-ROM) represents a considerable expense; specifically, the costs of the required memory and reading devices and, secondly, the costs of updating the map to keep it current. The possibility of shifting the task of recognizing road types to the data collection points and then reporting the results back to the vehicles is not a useful one, because of the extraordinary communications expense.
There is therefore a need to be able to automatically determine the road type being travelled on in the vehicle with sufficient accuracy and without great expense. This is useful in the framework of determining and collecting traffic data. Furthermore, it is also advantageous for traffic information to be received from drivers (e.g., via radios, mobile phones or other communications means) and stored so that it can be called up again at any time, as desired by the drivers, from a memory device. When a vehicle travelling a long distance is located on a highway, for example, traffic information about side streets is generally not of interest. For ergonomic reasons and in view of the required memory, it is useful to place limitations on the displayed or stored information. In order to limit the information, it would therefore be helpful to undertake an automatic selection of received information in the receiver device, so that only relevant traffic information, depending on road type, is displayed or stored.